Yes! You can do a soak cap of a toner with blue undertones. Soak capping is when you fully wet the entire head then mix the toner with shampoo and wash it in. this helps to get the toner on fast and evenly while diluting it helping to prevent over depositing. Because you are using a blue base on lighter hair you want to make sure to watch it and not leave it on extremely long as this may create a cast of color. Make sure to use nothing over 10% for your peroxide if you have any regrowth. If no virgin hair is present then you can use a 20% to open the cuticle allowing more lift of the unwanted tones.

I would go to a salon & tell them what you're trying to acheieve. It's more expensive than doing it yourself-but part of what you're paying for are their expertise. If money is an issue, look for a cosmetology school in your area on YELP. A student would be working on you, under the supervision/advice of an experienced instructor.